This invention relates to a disposable diaper provided with an indicator by which it is indicated visually from outside whether urination has occurred or not.
Japanese Patent Publication No. 1997-299401A discloses a disposable diaper comprising a liquid-pervious topsheet, a liquid-impervious backsheet and a liquid-absorbent core interposed between the top- and backsheets, defining a front waist region, a rear waist region and a crotch region extending between these waist regions, provided with an indicator which becomes visible and indicates an occurrence of urination from outside the backsheet when the front waist regions is wetted with urine.
The indicator comprises an ink layer which is disposed between the backsheet and the core and becomes visible when the ink layer is wetted with urine and an ink-covering layer which is disposed between the backsheet and the ink layer and put in close contact with the ink layer. The ink-covering layer contains a surfactant. The backsheet is made of breathable but liquid-impervious oriented plastic film containing fine particles of a titanium oxide, a calcium carbonate or a barium sulfate. This diaper is effective in that, when the indicator is wetted with urine, the surfactant contained in the ink-covering layer is dissolved in urine and the inner surface of the whitened backsheet is wetted with the urine and as a result the ink layer can be visually recognized through the backsheet.
Generally, it is unnecessary for a diaper that any third person other than a wearer's mother or a care personnel can detect whether urination has occurred or not. In the case of the diaper disclosed in the above-cited Publication, the ink layer becomes clearly visible upon urination, so urination is easily perceived by the third person. With this diaper, urination is pointed up by the third person and sometimes the diaper wearer's sense of pride may be injured.